1. Field of the Invention
The present invention relates to an apparatus for continuously dosing a patient with a liquid medicine at a moderate rate, by feeding it into a vein, urinary balloon or like organ of the patient. More particularly, the present invention relates to an apparatus that comprises a balloon accommodating an amount of liquid medicine to be supplied to the patient at a constant and moderate rate and in a continuous manner.
2. Description of Prior Art
A device of a certain type for continuously dosing a patient with an antibiotic, anti-cancer medicine or the like is disclosed in Japanese Unexamined Patent Publication Sho. 50-108790. This device comprises an elastic balloon which accommodates the medicine and tends to shrink to force it into the patient's body. A bladder for a liquid medicine dispenser is proposed in Japanese Patent Publication Sho. 63-51702. The bladder or balloon is made of a synthetic polyisoprene from which harmful additives are previously removed. A harmless antioxidant which is substantially insoluble in blood is blended with such a purified polyisoprene.
The present inventor proposed a few years ago an improved balloon also for use in a device to continuously and constantly exert pressure on a liquid medicine. This balloon is a length of natural rubber tube having its inner surface coated with a silicone resin membrane, and is of a composite structure in cross-section as shown in Japanese Unexamined Patent Publication Hei. 4-2360. The present inventor had intended that the silicone membrane would effectively prevent the migration of any additives in the natural rubber into the medicine.
Contrary to the present inventor's expectation, migration of natural rubber additives has been observed in liquid medicines one or more days after being filled into the balloon. Therefore, such usual additives have had to be initially removed from the natural rubber, before blending the natural rubber with an adequate amount of an antioxidant that is harmless and insoluble in blood, as disclosed in the Japanese Unexamined Patent Publication Hei. 5-115542.
However, such an intricate treatment of the rubber to remove usual additives and then to blend the rubber with an antioxidant takes a long time. Further, there is a likelihood that the quality of the treated rubber will undesirably vary depending on the conditions of treatment.
The present inventor has searched for a novel material for a balloon that would be composed primarily of an elastic rubber not previously treated (unlike the natural rubbers), but in which additives would nevertheless be inhibited from migrating into a liquid medicine.